The present invention relates to a method for segregating relatively light weight materials from relatively heavy weight materials.
In the case where first materials of relatively equal weight are mixed with second materials which are heavier or lighter than the first materials, techniques for segregating the first and second materials using a sifter or a flow of air have usually been employed. Such techniques are effective when the first and second materials are greatly different in weight from each other and are different in absorptivity. However, such techniques are generally ineffective in the case where unwanted materials to be removed are mixed with articles such as vegetables or fish which are soft and are likely to be intermixed or where unwanted materials adhere to other articles such as caused by static electricity.
The inventor has previously disclosed an apparatus for segregating unwanted materials from such articles in Japanese Utility Model Application No. 102778/1978. This apparatus will be described with reference to FIG. 1. A number of rollers 2 having relatively large diameter and to which is applied to a high voltage are rotatably arranged above a vibrating conveyor 1. The mouths of a suction device are provided near the upper portions of the rollers so that unwanted materials mixed with articles are picked up on the lower surfaces of the rollers and are then sucked away so as to separate them from the articles.
The apparatus according to this utility model performs quite excellently in that its work efficiency is high and the apparatus can treat processed foods which cannot be treated by the above-described conventional segregation techniques which use a sifter or a flow of air. However, the apparatus is still disadvantageous in that the weight or range of properties of unwanted materials segregated by the apparatus are somewhat limited. More specifically, the material to be removed must be light in weight so that it may be sucked onto the surface of the roller 2. When a material such as yarn or soft hair having a simple configuration is picked up by the roller (removal of such a material being often required in the field of food manufacture), it tends to remain stuck to the roller surface and therefore it is difficult to remove by suction with the result that the work efficiency of the apparatus is very much lowered. Furthermore, light weight materials often float between the conveyor and the rollers. That is, they are not picked up on the roller surfaces and are therefore not removed.